This invention relates to a cutting tool assembly having a resilient clamping mechanism and a replaceable insert retention member.
Cutting tools employing a resilient clamping mechanism for clamping cutting inserts are generally of relatively narrow thickness. For example, cutting operations such as grooving and parting off can be performed by a cutting insert retained in an insert pocket located between the clamping surfaces of upper and lower jaws of a relatively narrow holder blade. The holder blade is, in turn, generally clamped in a blade-retaining block. The holder blade is generally provided with a suitably designed opening, in the vicinity of the insert pocket whereby a relatively narrow bridging portion is formed enabling a limited degree of resilient displacement of one of the holder blade""s jaws relative to the other. Generally, the lower jaw is rigid and the upper jaw is resiliently displaceable. The opening can be of the form of an aperture, or a slot, or a slot terminating in an aperture. Examples of such cutting tools are disclosed in U.S. Pat. No. 3,785,021 and U.S. Pat. No. 4,580,930. A rotary slot-cutting tool employing a resilient insert clamping mechanism is disclosed in U.S. Pat. No. 5,059,068. The cutter body is disc-shaped and of relatively narrow thickness, with cutting insert pockets located around its periphery. As with the holder blade, an insert pocket of a rotary slot-cutting tool has two jaws between which an insert is clamped by means of the resilient force resulting from the bending of the clamping jaw.
Whether the cutting tool is a holder blade or a rotary slot cutting tool, the bending of the clamping jaw is obtained by manufacturing the insert pocket such that the distance between the clamping surfaces of the jaws is smaller than the height of the portion of the insert located between the clamping surfaces. Consequently, when an insert is located in the insert pocket, the clamping jaw is held in a bent position creating an elastic force by means of which the insert is clamped in position.
An example of a well-known problem with cutting tools of the type described above is that a forward region of the insert pocket can come into contact with the workpiece and consequently become damaged. This can be particularly problematic with rotary slot cutting tools, where the damaging of one or two insert pockets requires the replacing of the whole cutting tool. A solution to this problem is proposed in U.S. Pat. No. 4,604,004 in which there is disclosed a cutting tool assembly having a hard, wear resistant insert, a shim and a blade body. The shim has a recess that tapers towards its open end to springingly hold the insert. The blade body has a downwardly and rearwardly extending recess that tapers toward the blade body to wedgingly hold the shim and insert. Assembly of the cutting tool assembly is accomplished by first inserting the insert into the shim recess, after which the shim, with the insert mounted therein, is inserted into the blade body recess. As the cutting tool assembly is contacted with a workpiece, the insert and the shim are wedged further into the blade body recess, thereby increasing the positive retention of the insert and the shim. After a period of use, the insert and shim are removed from the body so that the insert can be replaced. The shim is removed from the blade body by inserting a screwdriver in a gap between the blade body and the shim and applying a prying action to the screwdriver. The insert is removed from the shim by inserting a screwdriver into a notch of the shim and then twisting the screwdriver.
A disadvantage of the cutting tool assembly disclosed in the ""004 patent is that after assembling the cutting tool assembly, the cutting edge of the cutting insert is not precisely located. As pointed out in the ""004 patent, the insert and the shim are further wedged into the blade body recess as the cutting tool assembly is contacted with a workpiece. This situation is particularly disadvantageous for rotary slot cutting tools where there are a plurality of cutting inserts spaced about the periphery of the tool and imprecise location of the cutting edges of the cutting inserts results in inefficient cutting operations in which some of the inserts participate more in the cutting operation than others.
In the ""004 patent the member in which the cutting insert is mounted is referred to as a xe2x80x9cshimxe2x80x9d. In the following description and claims the member in which the cutting insert is mounted will be referred to as an xe2x80x9cinsert retention memberxe2x80x9d.
A further disadvantage of the cutting tool assembly disclosed in the ""004 patent is that, the shim is not secured to the blade body. This can be especially problematic if the shim is used in a rotary slot-cutting tool, since there is nothing to prevent the shim from becoming displaced during a slotting operation. U.S. patent application Ser. No. 09/458,675, filed Dec. 10, 1999, provides a cutting tool assembly having a replaceable insert retention member with a resilient clamping mechanism that overcomes the above mentioned disadvantages.
However, the prior art does not provide means for ensuring that a cutting insert cannot become completely dislodged and even fly out of the insert pocket under the influence of centrifugal forces. A situation that can be particularly dangerous when operating at high speeds.
It is an object of the present invention to provide a cutting tool assembly having a replaceable insert retention member with a resilient clamping mechanism that is designed to ensure that a cutting insert is securely retained by the insert retention member in such a way that it cannot become completely dislodged and possibly fly out of the insert pocket under the influence of centrifugal forces.
The present invention is directed to a cutting tool assembly, comprising a tool body portion and at least one cutting portion at a forward portion of the cutting tool assembly, the at least one cutting portion comprising a tool clamping portion, and an insert retaining member. The insert retaining member is configured to retain a cutting insert, when such cutting insert is present.
The tool clamping portion comprises a tool base jaw having an upper side constituting a first clamping surface; a tool clamping jaw having an upper side and a lower side, the lower side constituting a second clamping surface, the tool base jaw and the tool clamping jaw having a gap therebetween for resiliently receiving the insert retaining member, the gap having a given rearward linear extent (L3); a first slot extending in a generally rearward direction from a rear section of the gap, the first slot terminating in an aperture, the gap together with the first slot and the aperture forming an insert retaining member pocket having a given rearward linear extent (L2); a forwardly facing first location surface; and a second slot extending generally rearwardly from a gullet bordering the upper side of the tool clamping jaw, the second slot having a given rearward linear extent (L1).
The insert retaining member comprises a base jaw having a lower side constituting a first clamping abutment surface for abutting the first clamping surface, and a clamping jaw having an upper side constituting a second clamping abutment surface for abutting the second clamping surface, the base jaw and the clamping jaw defining therebetween an insert pocket for receiving a cutting insert; and a rearwardly facing second location surface wherein, when the cutting tool assembly is assembled, the second location surface of the insert retaining member abuts the first location surface thereby precisely locating the insert locating member in the gap.
In one aspect of the invention, the rearward linear extent (L1) of the second slot may be much less than the rearward linear extent (L2) of the insert retaining member pocket (L1 less than  less than L2).
In another aspect of the invention, the rearward linear extent (L1) of the second slot, may be less than the rearward linear extent (L3) of the gap (L1 less than L3).
In yet another aspect of the invention, the first location surface may be located at a rear section of the gap adjacent the first slot and oriented substantially perpendicular to the first and second clamping surfaces. Furthermore, the second location surface may be located to the rear of the base jaw of the insert retaining member. The insert retaining portion may further comprise a securing portion to which a securing member can be removably attached for securing the insert retaining member in position in the gap between the tool clamping jaw and the tool base jaw of the tool clamping portion. Additionally, the securing portion may be an elongated portion of the insert retaining member extending in a generally rearward direction and capable of passing through the first slot. The securing member may be of a general trapezoidal shape, having a forward face and a rear face, and wherein when the insert retaining member is retained in the gap in the tool clamping portion, the securing member is received in a recessed region in the elongated portion of the insert retaining member, the recessed region having a shape generally similar to that of the securing member, the aperture has two rearwardly facing spaced apart abutment surfaces adjacent the first slot and the elongated portion of the insert retaining member has a forwardly facing rear abutment surface, the securing member being provided with a countersunk through bore with a first longitudinal axis and the recessed region being provided with a screw threaded bore having a second longitudinal axis, the first and second longitudinal axes being relatively displaced one with respect to the other in a manner so that when a countersunk head screw is placed in the countersunk through bore and is screwed into the screw threaded bore the forward face of the securing member abuts the two rearwardly facing spaced apart abutment surfaces and the rear face of the securing member abuts the forwardly facing rear abutment surface of the elongated portion, thereby ensuring that precise location of the insert retaining member is maintained.
In yet another aspect of the invention, the upper side of the tool base jaw of the tool clamping portion may be substantially parallel to the lower side of the tool clamping jaw of the tool clamping portion. Furthermore, the first and second clamping abutment surfaces may taper towards the rear of the insert retaining member forming therebetween a taper angle (xcex1). The taper angle (xcex1) may be approximately 2xc2x0.
In another aspect of the invention, the base jaw and the clamping jaw of the insert retaining member have, respectively, first and second insert abutment surfaces that taper towards a forward end of the insert retaining member at a given taper angle, and the cutting insert has an upper surface and a lower surface, the upper surface comprising two sections, a forward section and rear section, the forward section of the insert upper surface and the lower surface taper towards a forward end of the cutting insert with a taper angle substantially equal to the taper angle between the first and second insert abutment surfaces of the insert retaining member. The rear section, of the upper surface, and the lower surface may taper towards a rear end of the cutting insert.
In yet another aspect of the invention, the insert pocket may be provided with an aperture extending from a rear section of the insert pocket in a generally rearward direction.
Furthemore, the cutting tool assembly may be a rotary slot cutting tool in which the rearward linear extent of the gullet is much less than the rearward linear extent of the insert retaining member pocket.